Nose gear down lock



J1me 13, 1950 CLARK ET AL 2,511,528

NOSE GEAR DOWN LOCK Filed Aug. 5, 1948 3 Sheets-Sheet l K INVENTOR.

1/0): 5?. 61:2 rK Faber? D. fickz" June 13, 1950 J. R. CLARK ET AL 2,511,528

NOSE GEAR DOWN LOCK Filed Aug. 5, 1948 3 Sheets-Sheet 2 INVENTOR. John R. Ciark Rober? 1D. TzcZieTZ KTFOR 2255/ June 1950 J. R. CLARK ET-AL 2,511,528

' NOSE GEAR DOWN LOCK Filed Aug. 5, 1948 3 Sheets-Sheet 3 John R. (Jim-k BY Faber] D- 7761M? Patented June 13, 1950 NOSE GEAR DOWN LOCK John H. Clark and Robert D. Pickett, Stratford,

Conn., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application August 5, 1948, Serial No. 42,664

6 Claims. (Cl. 244102) This invention relates to aircraft alighting gear and more specifically to an improved down lock for the nose gear of a tricycle type aircraft landing gear arrangement.

It is an object of this invention to provide a ground lock for the nose landing gear of an airplane equipped with a tricycle landing gear which will prevent any inadvertent retractions of a nose gear when the airplane is on the ground.

It is a further object of this invention to provide an improved down lock having a manual release that will permit the nose landing gear to be retracted when the airplane is on the ground.

It is a still further object of the invention to provide an improved down lock mechanism which includes an adjusting mechanism for insuring a positive firm fit of the lock elements.

These and other objects of this invention will become apparent from the following detailed description of the drawings wherein a preferred embodiment is illustrated.

In these drawings,

Fig. 1 shows an aircraft with a tricycle type landing gear including a nose gear embodying the down lock mechanism of this invention;

Fig. 2 is an isometric view of a nose landing gear incorporating the down locking mechanism of this invention;

Fig. 3 is a detail side elevation of the down lock mechanism indicating the connections with the locking links of the landing gear;

Fig. 4 is an exploded view of the locking mechanism.

Referring to Fig. 1, an airplane indicated at H) is supported on the ground by a main landing gear l2 and nose gear M which incorporates the down lock mechanism of this invention. The landing gear is adapted to be retracted into the aircraft structure in a manner well known in the art.

Referring now to Fig. 2, the nose landing gear indicated generally at M is pivoted on its upper end on bar I8 which is firmly secured to aircraft structure and forms the support for the flanges 20 and 22 which are integral with the boss 24. The usual oleo shock strut 26 is firmly secured to the boss 24 and carries an extensible member 30 which telescopes therein in the usual manner. The lower end of the member 30 carries a yoke 32 which can swivel thereon and to which is secured a tire and wheel assembly 34. A clamp 36 fastened to, the bottom of telescoping member 3|] forms the lower connection of a scissors 38 at point 40. The scissors 38 have their upper 2 end pivoted to the lower end of the shock strut 26 by clamp 42 which carries a connecting rod 44 thereon while the scissors elements are also pivotally connected together at-46. The rod 44 has welded thereto an arm 48 which at its free end carries a pin 50; the pin 50 being slidably connected to the upstanding rod 52 by engaging the slotted connection 54 which depends from the rod 52. The upper end of rod 52 is pivotally secured to a bell crank 56 at 58 by the usual forked connection 60. An integral collar 62 on the middle section of strut 26 provides the support for one end of the right-hand support toggle link 64 and the identical left-hand support toggle link 65, the lower end of the toggle 64 being pivoted at 66 while the lower end of toggle 65 is connected to the flange i6 and rod 12 adjacent the bell crank 56 in a manner to be described in connection with Fig. 4. The upper ends of the toggles 6G- and 65 are pivotally connected to legs of a member 61 which is pivoted to aircraft structure at points $8.

A rearwardly disposed U flange it on the collar 82 forms a bearing support for a shaft 12 which passes through the extending portions of flange l0 and is fixed to the hook M. The pin 12 extends through another flange 16 of collar 62 in a manner which permits bell crank 56 to be firmly attached thereto on the outboard side of flange 16. A spring 18 is fastened to the free end of bell crank 56 at 80 and tends to bias the bell crank 55 in a clockwise direction thereby tending to rotate shaft 12 and its integral book 14 into a position to immediately engage a latch element I96 when the gear is in the extended position. The other end of spring [8 is fastened to suitable aircraft structure. The parallel flanges it each carry a lip 82 on their aft arcuate surfaces which, as seen better in Fig. 2, engages a cross piece 84 bolted to the hub of the hook 14 for purposes of limiting the rotational movement of the hook. The configuration and. position of the cross piece 84 is more clearly shown in Fig. 4.

Another collar 86 is secured to the upper per-.-

tion of the oleo strut 26 adjacent the boss 24 and carries a pair of flanges 88 extending aft therefrom which form the support for a pair of locking toggle links 90.. The relatively free ends of the links 90 are attached by means of a pair of toggles 94 to the support toggle links 64 and 65 strut 9G is provided which is pivotally secured at 98 to aircraft structure while its piston rod I is secured to the locking links 90 at I02 spaced from the axis of pivotation of the links 90. Thus it can be seen that as the piston rod IIlll retracts, the locking links 90 will rotate in a counterclockwise direction thereby breaking connection between toggle links SE! and 94 from an in-line position. As this locking link arrangement is.

broken the supporting toggle 64 is also caused to rotate in a counterclockwise direction thereby moving the toggles 64 and the pivotable member 51 from an in-line to a broken position. 'Further actuation of the strut 56 will then tend to rotate the entire landing gear gabout the bar I8 toward a retracted position.

The locking links 90 carry depending parallel flanges I96 which have their free ends firmly connected by the aforementioned latch'element I66 which is normally engaged by the hook 14. As best seen in Fig. l, the latch element IDS is threaded at both ends and has an eccentriccam surface IIi'i which can be rotatably adjusted in order to obtain a tight contact between the hook .14 and the cam surface lIl'I. When this adjustment is made the toothed wheel I09. .which is threaded and pinned onto one end of the latch element IDS, is locked in place by screw III which is threaded into one of the depending flanges I94. When thelanding gear is in the extended position the latch element IE5 is in a position to receive the internal arcuate portion jof the hook I4 so that when the latter is rotated c ver the cam surface I01 the landing ear will .be positively locked down.

in operation then when the aircraft is on the ground and resting on the landing gear, the oleo strut is partially compressed. thereby decreasing the angle between the elements of scissors 38. .Since the arm e8 (Fig. 2) is attached to rod 46, which is also rigidly attached to the upper element of thescissors 38, any motion of the scissors will impart motion to the arm (l8 and its integral pin Sil the latter being permitted to slide in the slottedfconnectioni l. Inasmuch as thespring ,IS causes the bell crank 56 to be biased in clockwise directionthe hook M will accordingly engage the bar I BE and this engagement will be maintainedat all times when the aircraft the ground and the oleo strut is at least partially on ressed. Therefore, while the air- $9 and link 9'! will remain effective to prevent the toggle connections between 90 and I02 and between 65 and-the member 61 from being gnovedfrom an in-line to a broken position.

,.A:fter the aircraft becomes airborne the oleo strut extends to its fully extended position due .to relieving the weight of the aircraft therefrom and due to theweight of the tire and wheel 34 acting downwardly thereon. During extension of theoleo strut-the angle between the elements of scissors 38 becomes greater thereby imparting clockwise rotationalmovement to the rod 44 and integral arm. 48 to cause thepin 50 to ride to the lower end of ,slot of theconnector .54. Further downward movement of the pin 51) will im art similar movement to the connector 54 and the rOdJTZtherebv rotating bell crank 56 counterclockwise against the tension of the sprin Since the bell crank 56 and the hook 74 are fixed to shaft I2 the hook will also be rotated counterclockwise out of engagement with the latch element Hi6. Of course, when the arcuate portion of the hook I4 is free'of the latchelement I06 the locking link 99 vis free to .move when the piston rod Hill of the strut 96 commences to retract.

In modern jet or similar aircraft it is often desirable to direct the jet exhaust at an upward angle from the horizontal hence it is the practice to mount a small caster wheel on the fuselage adjacent the nose and to retract the nose gear so that the aircraft assumes a nose down or kneeling position. Also, this same procedure has been adopted at times where a group of aircraft are parked, at close quarters within a con fined area. Further, since nose gears at times have oleo struts which extend and contract through large ranges it is not always desirable .froma safety standpoint to jack up the airplane extre ely high during routine maintenance reon tests in order to fully extend the strut "gear unlock position. Therefore it is necessary that some manually operated mechanism be available to disable the nose gear down look when the weight of the airplane is on the gear or when the ,oleo strut is not fully extended.

Tothi's end the 'rod 52' may be manually pulled in a downward direction by groundpe r'sonnell 'As rod S Z is pulleddownwardly the slot in connection 574 will slide freely over pin 50 and the bell crank the shaft 12 and the hook M will be caused to rotate against the bias'of spring I8 to disengage the hook from the latch element I05 in the manner as if the oleo strut were extended. After rod 52 is pulled downwardly sufiiciently the lever I20 (Fig. 4) which is pivoted on dance I6 of collar 52 can be rotated to bring the leg I22 into'a position to contact the lug I24 of hell crank lit thus preventing the bell crank 56 from lrotatingback in response to the bias of spring I8. The lever I an is serrated on its inner'bearint surface I26 for cooperating with corresponding serrations I28 on thepivot bearing I39 on flan e A spring I3 2 biases the lever' I 20 against the serrations I28 thereby preventing the le er 53 from slipping. A stop I 49 is also provided on the lever I20 so that its lock position can he pivotallvidentified during rotational movements.

.Since the particular unlocking action 'of th landinggear locking linkage and supporting linkage is dependent upon the initial movements of the actuating strut. the landinggear will not be retracted until such time as the piston rod begins to retract sufiiciently into theactueting strut so that the inline position 'of the various toggle links may be broken. This is an additional safety factor in that 'as'the actuatin sturt 95 is ordinarily operated by hydraulic fluid and in the event of failure of the hydraulic sy temthe lockin effect of the links scans l'will still bem aint ained.

As a result of this invention an improved. aircraft nose gear retracting mechanism has been provided which not onlylprevents inadvertent re traction of the gear when the airplane is'on the round but also provides, a means for manually disabling the gear down lock in the event that it is desired to retract the gearjwith the weight of. the airplane thereon. Further with this manual disabling mechanism it is inot necessary to jack unthe airplane to such a height so as to fully extend theoleo strut when it"is desired to'test thelanding gear through a cycle of operation.

Further as a result of invention a positiv .acting mechanism has bfe en provided which is simple in operationand constructionand requires a minimumof maintenance. Although only one embodiment of this invention has been described and illustrated inTthe drawings, it will be obvious that various changes and modifications can be made in the structure and arrangement of the parts without departing from the scope of this novel concept.

What it is desired to secure by Letters Patent 1s:

1. In a landing gear for aircraft including an oleo strut pivoted at its upper end to structure of the aircraft and carrying at its lower end a ground engaging member, retracting mechanism comprising a locking toggle, an actuating strut connected to said toggle, a support toggle piv otall connected to said oleo strut and to fixed structure of the aircraft, an operative connection between said locking toggle and said support toggle for locking the latter in a gear xtended position, latch mechanism 'operatively connected to said ground engaging member for maintaining said locking toggle in the locked position in response to engagement of said member, and manual means for disabling the said latch mechanism when said member is engaged to permit retraction of said gear.

2. In a retractable landing gear for an aircraft having a telescoping oleo strut pivotally connected at one end to aircraft structure and at its other end carrying a ground engaging member, an actuating strut for extending and retracting said gear, a support toggle pivotally connected at its upper end to aircraft structur and at its lower end to said strut intermediate the ends of the latter. a locking toggle pivotally supported at the upper end of said oleo strut and having a connection to said support toggle, a latch member fixed to said locking toggle, a latch engaging member pivotally supported on said oleo strut and operative in response to the telescoping movements of said strut, said latch engaging member normally maintaining said locking toggle in the gear extended position while said ground engaging member is engaged, and manual means for disengaging said latch engaging member to permit said toggles and said gear to be moved to the gear retracted position while said ground engaging member is engaged.

3. In a landing gear mechanism for aircraft comprising an extensible oleo strut having a support pivotally connected to the airplane, actuating mechanism for extending and retracting said gear including a support toggle and a locking toggle operatively connected to said gear and said actuating mechanism, cooperative detent means carried by said locking toggle and said oleo strut for engageably locking said locking toggl in response to contraction of said oleo strut, manual means for actuating said detent means to unlock said locking toggle while said oleo strut is contracted, and a latch for maintaining said manual means in the unlocked position of said detent means while said oleo strut is contracted.

l. In a landing gear mechanism according to claim 3 wherein the detent means includes a resilient member having an operative connection to said locking toggle and said oleo strut for biasing said detent means into the engaged position.

5. In an aircraft landing gear mechanism having a telescoping shock absorbing unit pivotally supported at its upper end to structure of the aircraft and carrying at its lower end a ground engaging member, a power actuating strut for extending and retracting said landing gear, a support toggle having one end pivotally connected to structure of the aircraft and its other end to said unit, a locking toggle pivotally connected to said support toggle and said unit for normally locking said support toggle in the gear extended position, a latch fixed to said locking toggle, a latch engaging member supported on said unit and operatively connected to said ground engaging member, said latch engaging member adapted to maintain said locking toggle in the gear extended position upon engagement of said ground engaging member, means for releasing said latch engaging member to permit retraction of said gear in response to disengagement of said ground engaging member, manual means for disengaging said latch engaging member to permit retraction of said gear when said ground engaging member is engaged, and detent means for locking said manual means in the disengaged position of said latch engaging member.

6. In a landing gear mechanism for an aircraft comprising an oleo strut carrying a ground engaging member at its lower end and having its upper end pivotally supported to structure of; the aircraft, actuating mechanism for moving-said ear between extended and retracted a support toggle pivoted at on end to aircraft structure and at its other end to said strut, a look ing toggle pivotally interconnecting said support toggle intermediate its ends to said strut, said locking toggle having an operative connection to said actuating mechanism and operative to unlock said support toggle in response to initial movements of said actuating mechanism toward a gear retracted position, a latch member carried by said locking toggle, a latch engaging member carried by said strut and operatively connected to said ground engaging member for maintaining said locking toggle in the locking position in response to engagement of said ground engag ing member, said latch member including an adjustable cam for insuring a tight engagement with said latch engaging member, manually operated means for disengaging said latch engaging member when said ground engaging member is engaged, and a locking element carried by said strut for locking said manually operated means in the disengaged position of said latch enga in member.

JOHN R. CLARK. ROBERT D. PICKE'I'I.

REFERENCE S CITED The following references are. of record in the file of this patent:

2,427,885 Turansky Sept. 23, 194'! positions. 

